This invention relates to a method of attaching bus bar(s) to a coating (e.g., low emissivity coating) in the context of a vehicle window (e.g., vehicle windshield), or other heatable window (e.g. IG architectural window unit). In particular, certain embodiments of this invention relate to a method of heating at least a conductive bus bar(s) in a manner such that a portion of the bus bar(s) bleeds down through at least one dielectric layer of the coating and ultimately contacts at least one electroconductive layer(s) of the coating.
Heatable windows are known in the art. For example, see U.S. Pat. Nos. 4,668,270; 5,434,384; 4,782,216; and 4,820,902, the disclosures of which are all hereby incorporated herein by reference. See also WO 88/06095. Heatable windows conventionally include first and second conductive bus bars in electrical contact with a transparent conductive coating including an electroconductive layer. The electroconductive layer generates heat when electric current is passed therethrough. In such a manner, the window may be defogged and/or snow/ice may be melted from vehicle windows such as windshields, backlites, sidelites, and/or the like.
Typically, in the context of such articles, the electroconductive layer is deposited directly onto and over the conductive bus bars in order to establish an electrical connection between the bus bars and the electroconductive layer. However, this is problematic when the coating includes a dielectric layer(s) desired to be positioned between the bus bar(s) and an electroconductive layer of the coating. In such instances, the presence of the dielectric layer between the bus bars and the electroconductive layer could prevent a good electrical connection which is desired between the bus bars and the electroconductive layer.
In an effort to solve this problem, U.S. Pat. No. 5,332,888 illustrates a film stack (i.e., coating) deposited over top of bus bars. However, the bus bars are designed to have a roughened or jagged upper surface. As a result, jagged points at the tops of the respective bus bar(s) project through lower dielectric layer(s) of the coating and make electrical contact with the conductive silver (Ag) layers of the coating. Unfortunately, this is problematic because (i) it is not always desirable to have jagged shaped bus bar(s), and/or (ii) this requires the bus bar(s) to be placed on the substrate prior to the deposition of the coating stack which is not always desirable for a variety of processing reasons.
In view of the above, it will be apparent to those skilled in the art that there exists a need in the art for a more efficient way of establishing an electrical connection between bus bars and an electroconductive layer(s) of a coating. There also exists a need for enabling a multi-layer coating to be deposited on a substrate, and thereafter establishing an electrical connection between a conductive layer(s) of the coating and a pair of bus bars.
An object of this invention is to provide an efficient method and/or system of establishing an electrical connection between a pair of bus bars and a conductive layer of a multi-layer coating. The multi-layer coating may be a low-E (i.e., low emissivity) coating in certain embodiments of this invention, although all embodiments are not so limited.
Another object of certain example embodiments of this invention is to provide a method for electrically connecting at least one bus bar(s) to an electroconductive layer of a multi-layer coating, wherein the multi-layer coating has been deposited on a substrate prior to deposition of the bus bar(s) on the substrate.
Another object of example embodiments of this invention is to provide a heatable vehicle window (e.g., windshield, sidelite or backlite) including a multi-layer coating formed on a substrate. The multi-layer coating includes at least one dielectric layer and at least one conductive layer. A pair of bus bars are deposited on the substrate over the coating, so that at least the dielectric layer is provided between the bus bars and the conductive layer(s). In order to create an electrical connection between the bus bars and the conductive layer(s) of the coating, the bus bars and/or coating is/are heated to a temperature sufficient to permit the bus bars to reach molten or semi-molten flowable form. Portions of bus bar material then flow down through at least the dielectric layer of the coating (i.e., forming a contact hole in at least part of the coating) so as to contact the coating""s conductive layer(s). After cooling of the newly formed bus bars, the window may be selectively heated by passing current through the conductive layer(s) via the bus bars.
Another object of this invention is to fulfill one or more of the above-listed objects.
Generally speaking, an example embodiment of this invention fulfills one or more of the above-listed objects by providing a method of making a heatable vehicle window, the method comprising:
depositing a multi-layer coating on a substrate, the multi-layer coating including at least one dielectric layer and at least one conductive layer;
forming first and second conductive bus bars on the substrate over the coating such that the bus bars as formed are not in electrical contact with the at least one conductive layer of the coating; and
heating at least the first and second bus bars to a temperature sufficient to cause the bus bars to flow or migrate through the at least one dielectric layer creating a contact hole therein and make contact with the at least one conductive layer, so that after cooling the first and second bus bars are in electrical contact with the at least one conductive layer of the coating.
Another example embodiment of this invention fulfills one or more of the above-listed objects by providing a method of making a heatable window, the method comprising:
depositing a multi-layer coating on a glass substrate, the multi-layer coating including at least one dielectric layer and at least one conductive layer;
forming at least one conductive bus bar over the coating such that the dielectric layer is located between the bus bar and the at least one conductive layer; and
heating the bus bar to a temperature sufficient to cause the bus bar to bleed through the dielectric layer and contact the at least one conductive layer, so that after cooling the bus bar is in electrical contact with the at least one conductive layer of the coating.
Another embodiment of this invention fulfills one or more of the above-listed objects by providing a heatable window (e.g., vehicle window, architectural IG window, or the like), comprising:
a glass substrate;
a multi-layer coating provided on said glass substrate, said coating comprising a first conductive metal layer located between first and second dielectric layers;
first and second conductive bus bars formed over said coating so that the coating is located between the glass substrate and the bus bars; and
wherein a run-off or bleeded portion of each of said first and second bus bars extends through a respective contact hole in at least said first dielectric layer so that each of said first and second bus bars is in electrical contact with said first conductive metal layer of said coating.
This invention will now be described with respect to certain example embodiments thereof as illustrated in the following drawings, wherein: